Polymer composition comprising 50-99% by weight of a thermoplastic resin or a blend of thermoplastic resins, 1-50% by weight of a graft copolymer comprising a rubbery graft base upon which one or more monomers have been grafted, the quantities of (a) and (b) being calculated with respect to the sum of (a) and (b) taken together; and a phosphorescent pigment with an aluminate matrix expressed by M-Al, in which M is at least one metal element selected from calcium, strontium and barium and Al represents an aluminate group. The aluminate group can be for example a Al.sub.2 O.sub.4 -group. The invention also relates to concentrates that are suitable for making the polymer composition of the invention.